"On this earth there are pestilences and there are victims ... one must refuse to be on the side of the pestilence"—Camus

March 24, 2015

On his Avian Flu Diary, Mike Coston has posted HK CHP Avian Flu Report: 2 Weeks Without An H7N9 Case Report. He puts the lull in the context of the first two H7N9 seasons, and offers some well-informed speculation on whether the outbreak has really ended, or is just under-reported by the Chinese authorities.

To study human-to-human transmissibility of the avian influenza A (H7N9) virus in China, household contact information was collected for 125 index cases during the spring wave (February to May 2013), and for 187 index cases during the winter wave (October 2013 to March 2014).

Using a statistical model, we found evidence for human-to-human transmission, but such transmission is not sustainable. Under plausible assumptions about the natural history of disease and the relative transmission frequencies in settings other than household, we estimate the household secondary attack rate (SAR) among humans to be 1.4% (95% CI: 0.8 to 2.3), and the basic reproductive number R0 to be 0.08 (95% CI: 0.05 to 0.13). The estimates range from 1.3% to 2.2% for SAR and from 0.07 to 0.12 for R0 with reasonable changes in the assumptions.

There was no significant change in the human-to-human transmissibility of the virus between the two waves, although a minor increase was observed in the winter wave. No sex or age difference in the risk of infection from a human source was found.

Human-to-human transmissibility of H7N9 continues to be limited, but it needs to be closely monitored for potential increase via genetic reassortment or mutation.

In this study, an international team of scientists led by Yi Guan of Hong Kong university monitored the evolution and spread of H7N9 over 15 cities across five provinces in China.

By collecting and sequencing a large number of samples, they found that the H7N9 virus is mutating frequently, acquiring genetic changes that might increase its pandemic potential.

A large number of new genetic variants of the virus have become established in chickens and have spread across the country, probably because of poultry trade movement, they said.

Flu experts not directly involved in the research said its findings were interesting but did not necessarily show the H7N9 was changing in ways that made it more likely to develop into a pandemic flu strain.

"What we don't know from this paper is the significance of all these mutations that are accumulating as the virus persists and spreads," said Wendy Barclay, an expert in flu virology at Britain's Imperial College London. "This is especially relevant for human health -- does any of this change the pandemic potential of the virus?"

In its latest update on the flu strain, the Geneva-based WHO said it "continues to closely monitor the H7N9 situation" and conduct risk assessments.

"So far, the overall risk associated with the H7N9 virus has not changed," it said.

Yi Guan's team, however, said their analysis pointed to a need for heightened vigilance of H7N9 and for curbing direct human contact with live poultry at markets.

"Permanent closure of live poultry markets, central slaughtering and preventing inter-regional poultry transportation during disease outbreaks are needed to reduce the threat of H7N9 to public health," they wrote.

As soon as H5N1 re-emerged in 2003, the worry was that it would learn how to go H2H2H—from one human to another, and then to a third. It certainly has the potential, and if it maintained its deadliness after such a mutation, we would be in big trouble.

The same can be said of H7N9, especially since it doesn't especially bother poultry; you know H5N1 is around when the birds go argh-plop, but you don't know about H7N9 until your customers get sick from your tasty, freshly slaughtered birds. By that time, who knows where all your other birds have ended up, and which of them might have a mutation that lets it flourish and spread in humans.

But Yi Guan and his colleagues have a tough job ahead of them in a free-market China where the customers insist on buying live chickens, and only grudgingly accepts wet-market shutdowns.

Scientists have warned that the H7N9 variant of bird flu could severely mutate and urged health authorities to implement strict measures to prevent this, including closing live poultry markets and introducing centralised slaughtering.

A research team led by the University of Hong Kong found that H7N9 gene combinations were constantly changing and spreading on the mainland. Researchers are particularly worried that the strain could mutate in a way that made human-to-human transmission possible The research, conducted in collaboration with mainland, US and Australian health authorities, was published in the international journal Nature.

H7N9 was first discovered in eastern provinces in March 2013. But scientists are unclear how the virus re-emerged in August of that year and then again late last year. A total of 638 confirmed human cases of H7N9 have been reported globally since 2013, including 229 deaths, according to figures from the World Health Organisation.

Researchers collected 23,000 samples from the respiratory tracts of chickens and ducks in 15 cities in five provinces between October 2013 and July last year. They identified three geographically distinct groups with 48 gene combinations, which they said indicated that the disease had changed rapidly and spread.

"H7N9 is active … The virus is possibly more infectious and leading to transmission among humans," said Dr Maria Zhu Huachen, an assistant professor at HKU's school of public health.

Chickens appear to be the direct source of H7N9 cases. No trace of the virus was found in the samples taken from ducks.

"The virus might have been spread by trade … We saw previously that the number of patients dropped when [wet] markets were closed," Zhu said, adding that the virus could spread further if no measures were taken. "The virus could spread to Vietnam and Cambodia through the southwestern provinces."

Zhu said avoiding contact with live chickens was crucial in stopping the spread of H7N9. "Chickens are dangerous as they are usually asymptomatic … Permanently banning chicken imports from the mainland is the safest course of action," she said.

The Centre for Health Protection (CHP) of the Department of Health (DH) today (March 9) received notification of 19 additional human cases of avian influenza A(H7N9) with the onset dates in the past five weeks prior to February 25 from the National Health and Family Planning Commission, and again urged the public to maintain strict personal, food and environmental hygiene both locally and during travel.

The patients comprise 13 males and six females aged from 3 to 76. Three of them (one man and two women) died and two (one man and one woman) were in critical condition. Eleven cases are from Zhejiang, three are from Jiangsu, two are from Hunan, one is from Fujian, one is from Guizhou and one is from Jiangxi.

The Centre for Health Protection (CHP) of the Department of Health (DH) is today (March 7) closely monitoring two additional human cases of avian influenza A(H7N9) in Guangdong (GD) notified by the Health and Family Planning Commission of GD Province (GDHFPC), and again urged the public to maintain strict personal, food and environmental hygiene both locally and during travel.

Situation in GD

According to the GDHFPC, the two male patients, aged 62 in Foshan and aged 57 in Jiangmen, were hospitalised for management in critical and serious condition respectively.

The activity of avian influenza viruses in the Mainland remains high this winter and cases in GD are on the rise. To date, 599 cases have been reported by the Mainland health authorities cumulatively since 2013, with 181 (30 per cent) from GD. In GD, 72 cases (40 per cent) with onsets since November 2014 were reported, including 13 from Shenzhen, eight each in Dongguan and Meizhou, etc (see Attachment for geographical distribution).

March 06, 2015

The Centre for Health Protection (CHP) of the Department of Health (DH) is today (March 6) closely monitoring an additional human case of avian influenza A(H7N9) on the Mainland, and again urged the public to maintain strict personal, food and environmental hygiene both locally and during travel.

According to the Health and Family Planning Commission of Anhui Province, a male patient aged 79 with poultry exposure before onset was hospitalised for management in critical condition.

March 05, 2015

The Centre for Health Protection (CHP) of the Department of Health (DH) is today (March 5) closely monitoring two additional human cases of avian influenza A(H7N9) on the Mainland, and again urged the public to maintain strict personal, food and environmental hygiene both locally and during travel.

According to the Health and Family Planning Commission of Anhui Province, two male patients aged 50 and 68 respectively with poultry exposure before onset, were hospitalised for management in serious condition.

March 01, 2015

The Centre for Health Protection (CHP) of the Department of Health (DH) is today (March 1) closely monitoring two additional human cases of avian influenza A(H7N9) in Guangdong notified by the Health and Family Planning Commission of Guangdong Province (GDHFPC), and again urged the public to maintain strict personal, food and environmental hygiene both locally and during travel.

According to the GDHFPC, two male patients aged 36 (in Foshan) and 45 (in Dongguan) were hospitalised for treatment in stable condition.

The Centre for Health Protection (CHP) of the Department of Health (DH) is today (March 1) closely monitoring two additional human cases of avian influenza A(H7N9) in Guangdong notified by the Health and Family Planning Commission of Guangdong Province (GDHFPC), and again urged the public to maintain strict personal, food and environmental hygiene both locally and during travel.

According to the GDHFPC, two male patients aged 36 (in Foshan) and 45 (in Dongguan) were hospitalised for treatment in stable condition.